The Field of Invention
The invention relates to an adjustable spanner comprising:    a pair of jaw arms, co-operating to move relative to one another, the co-operating jaw arms are each provided at their ends with a jaw, wherein two adjacent jaws constitute a spanner head,    a housing for receiving the co-operating jaw arms, wherein the ends of the jaws extend outside the housing,    the co-operating jaw arms slide longitudinally relative to the housing, thereby mutually tilting the jaw arms relative to one other due to the sliding, so that the jaws of the spanner head of the co-operating jaw arms move in opposite transverse direction relative to one other.
Description of the Related Art
This adjustable spanner is a constructive advantageous variant on the famous ‘English key’ or adjustable angle-head wrench. The screw adjusted spanner, by means of a worm gear, has a size-adjustable jaw width and can therefore, within certain limits, be adjusted to any size hex or square fastener head, nut or bolt, so that there is no need to have standby a large amount of fixed spanners or socket wrenches for a range of different fastener head sizes.
The adjustable spanner, however, has the disadvantage that it is difficult to accurately set the correct desired fit-size of the fastener head. Furthermore when the screw mechanism is worn out the set head size may wander off when exerting a torque force. With an improperly set jaw size the bolt or nut head may be damaged irreparably.